Caterpillars chew over plant defenses

A salivary enzyme is a key weapon in the evolutionary arms race between plants and animals.

David Bruce(
Apr 10, 2002

Arthropods that feed on blood secrete compounds in their saliva that act to neutralize the host defensive reaction, but it remains unclear if a similar mechanism operates in plant-feeding organisms. In 11 April Nature, Ron Musser and colleagues at the Department of Entomology, Penn State University, show that the Helicoverpa zea caterpillar releases glucose oxidase in its saliva that mitigates against the defenses of the tobacco plant Nicotinia tabacum (Nature 2002, 416:599-600).

Musser et al. ablated the saliva-secreting organ of the caterpillar (the spinnerets) of a group of H. zea caterpillars and placed them — and control, unablated larvae — in individual cages on the second uppermost leaf of N. tabacum for 24 hours (one plant per caterpillar). Analysis of leaves fed on by unablated caterpillars showed a 26% reduction in the level of nicotine — an inducible plant defense compound — (P<0.05)....

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